Hi, I just started to practice resin infusion and I made my bag with pleats just like the video tutorials show, I then found a leak on one of the pleats when pulling a vac down and a simple squeeze of the bag tape cured the leak.  After a few seconds the gauge went to full vac and the pump noise changed, I then clamped the vac line to do a drop test.  returning 20 mins later I noticed that the catch pot lid had leaked and the gauge had dropped so I sealed the lid and then pulled vac on the catch pot up to the line clamp.  Then I switched off the pump and opened the clamp to drop test the bag and the gauge stayed the same.

I did the infusion and took it slow and when the resin started going up the catch pot line I clamped off the line followed by the feed line.  After returning an hour or so later the bag had lost its vacuum so am I missing something very simple or do I keep scratching my head.

I have no experience of fibreglass or carbon work so I am looking to make mistakes and learn from them before actually taking on the project that I set out to do.

Cheers Lee

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Hi Lee

Hi Lee,

Thanks for the reply's, I will try and get my second mould finished and will bag it and try leaving it longer, but how do you guys normally locate micro leaks, thought about getting a leak detector but will it detect leaks that are unable to be heard by the ear. 

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It really is all about experience. You learn to spot a leak before you even pull the bag down. Quality materials help too, make sure you are using a nice soft and very tacky bagging tape. I used to use a General Sealants bagging tape that was so hard and non-tacky that you could remove it from the bag after use and roll it back up, freakin awful stuff. While using this, I thought a leak free bag was a myth, couldn't even get an envelope bag to seal! Changed over to the black Cytec stuff, and these days I very rarely have to do any checking for leaks, it all just seals so nicely. 

Thanks for the reply, I am using EC bagging tape and the everything I have came from them.  The tape seems fairly tacky but when inspecting the bag up close it did look like it had a tiny amount of damage.  will be trying another one later today.

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Hi guys, I have just layed up a mould and bagged it, but this time being super careful about having creases in the bag where it meets the gum tape, I pulled a vac on it and with a few small leaks quickly solved by pressing on the gum tape it seems to be holding vacuum. woohoo.

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Envelope bags for the win if possible.

Can save a whole lot of messing around, lay the bag on a flat surface lay down some gum tape on the edges seal one side of the bag then slip your mould into the bag with input/output silicone connectors in place with a bit of gum tape, then seal the second side. Install the input/output lines and job done, time for a drop test

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David Stevens
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what about using soapy water on the outside to look for leaks?

You don't want any water inside your bag, not your friend.